This invention pertains to display devices and, more particularly concerns display devices that are configured for use in page display, serial, sequential reading applications.
Display devices come in many shapes and sizes and can be implemented using different types of technologies. One particular type of display device is one that enables a user to read various types of materials such as text (e.g. books, magazines, and newspapers) maps, drawings, and the like, while maintaining a desirable degree of portability. For example, in recent times, there has been a push by the industry to provide so-called electronic xe2x80x9creadersxe2x80x9d so that users might be able to read an electronic version of a favorite book or newspaper.
The design of electronic readers requires an appreciation and consideration of several factors that directly affect the popularity and commercial marketability of the electronic reader. In order to meet the demands of very discriminating consumers, and to provide an economically sensibly-manufactured product, electronic readers should or must: (1) be small enough to be conveniently portable, (2) have a desirable degree of contrast so that the user can easily read content that is displayed by the reader, (3) have a high degree of resolution so that the images displayed by the reader are crisp and clear, (4) have low power consumption characteristics to reduce the overall footprint within the device of the power supply component as well as to provide a desirably long lifetime for a given power supply, and (5) have a low enough cost so that it can be widely available for purchase by many consumers.
There are different technologies that are available for manufacturing various types of display devices among which include CRT (cathode ray tube) technologies, LCD (liquid crystal display) technologies, FEDs (field emission display) technologies, and so called xe2x80x9cE-inkxe2x80x9d technologies, which employ microspheres having at least two reflectance states.
CRT technologies are limited, to a large extent, by the contrast that is able to be provided, the size requirements of the displays, the power consumption, resolution and cost. This technology is not a logical choice for conveniently portable electronic readers. LCD technologies typically have complicated electronics and display componentry and do not achieve a desired degree of resolution at a cost that is acceptable to compete in the display reader market. The same can be said of FED technologies.
There is a continuing unmet need for display readers that meet all or some of the criteria discussed above. It would be highly desirable to provide such a display reader that can display content from a number of various sources, such as the Web, a database, a server, and the like, and do so in a manner that satisfies or accommodates the needs of our biological system (i.e. eyes) for resolution, contrast, speed of image generation for reading and the like. Accordingly, the present invention arose out of concerns associated with meeting some or all of these needs.
Electronic display devices and methods are described. In one embodiment, an electronic display device comprises a housing and a display area within the housing to display content for a user. Memory is provided within the housing to hold data that is to be rendered into user-viewable content. An electrophotographic assembly is provided within the housing and is configured to electrophotographically render user-viewable content from the data that is held in the memory. A loop of material is disposed proximate the electrophotographic assembly and is configured to receive electrophotographically rendered content and present the content for user viewing within the display area. The electrophotographic assembly can use black toner and the loop of material is selected to provide a black/white contrast when used in connection with the black toner. In one embodiment, the electrophotographic assembly can render content at at least 300 dots per inch (dpi) and better. The display device is desirably sized so that it is portable and includes a power source, e.g. one or more batteries, to facilitate its portability and use abroad. In one embodiment, the electrophotographic assembly comprises an optical photoconductor (OPC) drum, a charge mechanism (e.g. a charge roller) to charge the optical photoconductor drum, a source of light energy (e.g. an LED array) to expose selected areas on the optical photoconductor drum, a developer mechanism to provide toner onto the optical photoconductor drum, and a transfer mechanism (e.g. a transfer roller) to effect transfer of the toner from the optical photoconductor to a print medium such as the loop of material.
Printing is effectuated by advancing or moving the loop of material through the electrophotographic assembly and electrophotographically forming an image on the loop of material. Such can be accomplished by electrostatically attracting toner onto the loop of material sufficient to provide a viewable image. Advantageously, the toner can be held in place on the loop of material using only electrostatic forces thereby obviating the need to permanently fuse the toner to the material. After the image is displayed for the user, the toner can be reclaimed off of the loop of material for reuse in providing additional images.